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What is the effect of salt on the temperature of water?
Question Date: 2018-04-26
Answer 1:

This is a really cool question! The effect of salt on the temperature of water depends on what temperature the water is.

In general, salt doesn't really change the temperature of water, unless its trying to boil or freeze. When the water tries to freeze, it will need to be colder than 0 degrees Celsius, and when it tries to boil, it needs to be hotter than 100 degrees Celsius. This is known as "freezing point depression (decreasing)" or "boiling point elevation (increasing)."

A fun application of this is why when it snows in the United States, people put salt on the roads. This salt helps to prevent the water from turning to ice as easily because by adding salt, the temperature outside needs to be colder to get the water to freeze!

Note from ScienceLine moderator:

The following link to our database has interesting information which will enrich this answer. However this information might be confusing for a 4th grader, so I suggest to read it in the company of a grown up.:
click here


Answer 2:

Salt increases the boiling point and decreases the melting point of water. That means if you add salt before heating some water on the stove, it will take longer to boil. Also, if you add salt onto ice, it will melt faster!


Answer 3:

Salt makes water boil at a higher temperature - water sticks to the salt ions, so they can't get out of the liquid as easily.

Salt makes water freeze at a lower temperature - it's probably harder for the water molecules to get organized into a solid state with all the salt ions messing up its structure.

I figured salt would also lower the temperature of water, because the water molecules sticking to the salt ions wouldn't be able to move around as fast, but I didn't know, and the stuff on google seemed to be about freezing and boiling, so I did an experiment:

I put water in a glass, and it was 70 deg Fahrenheit. I added a bunch of salt and the temperature dropped immediately to 68 degrees Fahrenheit. I stirred and stirred and the temperature stayed at 68 deg F. So, indeed, salt lowers the temperature of liquid water.

When I took the digital thermometer out of the water, the temperature fell lower and lower - the evaporating water was cooling the thermometer!


Answer 4:

Nothing. Salt doesn't affect water temperature. Salt does increase the temperature at which water boils, and lowers the temperature that water freezes, but does not affect the temperature itself.



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